Dust collector



Sept. 18, 1951 N. N. STEPHANOFF 2,568,032

DUST COLLECTOR Filed April 22, 1949 I as in 44 a H 10, an; T :g; 4s 4 4 l 4 \I\I\\TI I 12 M, 64

FIG. 4.

l INVENTOR. NICHOLAS N.. STEPHANOFF Patented Sept. 18, 1951 2,568,032 nusr' ootmoro e Nicholas =N5. stephafioir, oymwa; -Pa*.-, assi nar. to

0. H. Wheeler- Manufacturiiig cbmpafiy, Philadelphiai Pa.,. a, corporationor-Pennsylvania Kpplica'tion April 22; 1949'; "S'rialNb. 881989 This invention relates to dust "collectorsarid' has" particular reference to' a collectorora" type'capable of separating and collecting particles of" sizesorthe order of one micron.

Dust collectors of the cyclonetype have been commonly used for the colle'ctidn of smalPp'ar ticles but in general those which h'avebe'enpro vided are ineffective in securing a good separation of particles in the size range of one micron: In order to separate "very' fin'e particles high velocities of flow of suspensions are required todevelop greater centrifugal force; However, increaseof' velocities has not generally been 'possiblewith provide a collector capableof retainingavery high percentage of even the finest materials. 'In

accordance with "the invention there has'b'een secured better 'than" 99% cbuection of materials havingan average 'particle size of'theorde'rof one micron. Heretofore, such a"collectionhas been impossible in" a cyclone type collector, there having been usedbeyondsuch a collector a ba'g or sleeve-typecollectorto separate the residual 'particlesi- Oneofthe objects of the present inventionie" to provide a separator which does not have any ledgeor shelf on which material may rest to im pede-flow or to give rise to sudden spurtsof ma terial in the collector so as to overload" it.

A further'object of the present invention is to provide a collector in which'high'velocities maybe" used: to develop large centrifugal forces without; however; there being involved in connection t-with the high velocities any tendency to-pick up or maintain material-in suspension despite the centrlfugalseparati'ng forces 7 Still another object of the invention'is-to provide anarr'angement in the form "of an expanded chamber below'the collector to efiectstill more completesep'aration of the particles,'-this cham ber being sealed-removal of material therefrom being accomplished through a rotary valve or equivalent arrangement.

The foregoing-and etherobjects-particularly relating to details of construction and operation-- will becomeapparent from the following descrip-- 1 Glaiin. (01. 1 83- 83 tion read in conjunction with the accompanying drawings in which:

Figure 1 is an elevationshowing'a preferred embodiment of the inventionin apairo'f asso 5 ciate d collectors for the purpose of securingsepg aration of relatively large and relatively *sir'ialb particles;

Figure 2 is a plan view showing in particular the upper elements of Figure l;

Figure 3 is a section taken on the plane indi cate'd at 33 in Figurel;

Figured is a sectiontaken' on-the plane=indi catedat 44 in Figure 1 and Figure 5 is a section-showing an alternative form of a classifier element of'a collector.

The inlet 2 of the collector"arrangement-mus treated in Figure 1 receives a suspension'0f flhe' particles in an elastic-fluid 'suc'h' as'air or steair'i' and maybe connected, for example, aireeu'y'tt the outlet from a grinding mill; In viewor' 'the effectiveness of the present collectorin separat= ing very minute particles the mill used may be of the typee'ffectin'g grinding by the use ofhigh velocity elasticfluid jets, such mms being'eap'a ble of producing particle'sizes of the order of one" micron or'less. In general, of course, summin produce particles of a substantial-ranged si'z'es' and, in accordance with-"the specific disclosure herein, provision is made for the separation of" particles of different sizes, which separationds'" for many purposes, for example when it apartransverse cross section a generally spiral sha e' with the portion 6 of its circumference having a'j" ticularly necessary to insure that'oversi'ze parti-'-- cles are to be eliminated'from the final desired product or when separateuses areto be foundfor larger or'smaller particles, it beingfsometimes desirable that the particles should not be too small? greater radius than the portion 8'thereof. form may be-achieved, for example, by forming the volute chamber walls as segments of cylirid of successively decreasingradii. The 'radial'sec'-' tion of the chamber will, in general, approximate the form of an involute or spiral curve. The decrease of radius of curvature from 6 to 8 produces acceleration of the elastic fluid and the suspended particles therein. The volute chamber which is thus provided is superimposed on a conical section Ill with the provision of a top ledge I I filling the radial space between the lower edge of the volute and the top edge of the section I0. It will be noted that this ledge II does not constitute a shelf facing upwardly in the interior of the collector but rather provides merely a roof portion of the collector from which any particles engaging it would fall by gravity. This is in contrast with arrangements heretofore used providing internal upwardly facing shelves on which materials could collect as described above. It may be noted in brief that the arrangement results from having the top of the conical section II] of the same radius as the maximum radius of the volute chamber. I

Below the conical section IE! is a cylindrical section indicated at I2 which may have varying lengths depending upon the separating action whichis desired. As a downward continuation of the section I2 there is another conical section [4 having an outlet opening at I6.

The outlet opening I6 projects through an opening in the top cover ll of a chamber of relatively large diameter which comprises a cylindrical portion I8 and a conical lower portion 20. The cylindrical portion I8 is desirably of considerable heightand is illustrated as broken in Figure 1. As will be hereafter pointed out, the chamber comprising the portions I8 and 20 is one of relative quiescence and has an important function in aiding in the separation of the material. The separated material collects in the lower conical portion 20 and may be removed therefrom without disturbing the action of the collector through the medium of a conventional vaned rotary valve 22 from which it may pass through a connection 24 to a screw conveyor indicated at 26 by which it may be fed to a storage bin or directly to a point of use. The chamber should be sealed against loss of elastic fluid for most effective operation. It may be noted that it is quite impossible that solid material entering the chamber 1,20 could return again into cone I4, so that effective trapping of material therein is secured.

The end I6 of the cone l4 may extend substantially lower than illustrated into the upper portion of chamber I8, the extent of projection thereinto depending upon the materials involved.

Extending downwardly through the top of the volute chamber is a tube 28 which may be of downwardly tapered shape as indicated, opened at its lower end in the vicinity of the upper portion of the cylindrical section I2. As will be evident hereafter this tube may take a special form but in the instance illustrated the collector is of a type designed to effect removal of only relatively large particles in the first separation stage and in such case the tube 28 may be as described. The upper end of this tube contains externally at 30 in the way of a flared portion having a tangential outlet at 32 communicating with a pipe 34 which leads the elastic fluid containing finer particles to the second separating stage. The goose neck form of pipe 34 is desirable as it tends to promote segregation of the particles in suspension. This also eliminates vortical motion existing in the volute 30 from the flow to the second stage.

The second stage collector comprises a volute 40, a conical section 44, a cylindrical section 46 and a lower conical section 48, the latter communicating with the upper end of the chamber 50 through an opening in the top cover 49 thereof. The chamber 50 is similar to that provided by the portions I8 and 2a of the previously described quiescent chamber and the material separated therein may be removed through a rotary valve 52, connection 54 and screw conveyor 56 as previously described. The intake 36 of the second collector delivers its suspension through nozzle portion 38 into the volute 40 and the construction of all of the parts so far described of the second stage collector may be identical with those previously described in connection with the first stage.

The second stage collector, however, is shown as designed for the removal of extremely fine particles and for this reason in place of the tube 28 there is provided a tubular member 58 having a lower conical extension 64 opening at 62 into the interior of the conical section 48. The member constituted by 58 and 64 may project to any desired extent downwardly depending upon the particular size particles which are to be separated. For maximum separation effect it may extend downwardly to a point quite closely approaching the lower outlet from the conical section 48.

The tubular member 58,64 attains its highly effective separation characteristics by reason of annular exterior space, these flows being indicated by the arrows in Figure 4.

The upper end of the tubular member 58 is continued at 66 to an outlet chamber 68 having tangential communication at III with an exhaust conduit 12 which may communicate with the intake to an exhauster fan or blower 14, the action of which may be controlled by a damper indicated at Hi.

In the operation of the two stage collector which is illustrated the suspension of particles in the elastic fluid enters at 2 at fairly high velocity and takes a helical and downwardly flowing path inside the volute and the section I0. Due to the downward convergence of section It) the angular velocity of the flow increase and the larger particles of the material are thrown outwardly against the outer walls and are there separated. The elastic fluid carrying the smaller unseparated particles undergoes an upward reversal of flow into the tube 28. The vortex which is set up in the volute chamber and the section l0 continues in the form of a vortex through the sections I2 and I4 maintainin the separation of the particles already separated and effecting additional separations in the sections I2 and I 4. The

vortex, in fact, continues with increasing angular velocity down through the lower section I4 to'the extent that there appears below the exit opening I6 inside the upper portion of the chamber constituted by I8 and 20 a vortex which further insures separation of material into the chamber of relative quiescence, in the lower portion of which the material accumulates for removal through the valve 22.

The elastic fluid carryin now the finer particles in suspension passes to the second separator through the connection 34 wherein there is set up a vortex in the volute chamber 40, the sections 44, 46 and 48, and in the upper end of the chamber 50 immediately below the exit opening at the bottom of the conical section 48. The angular velocity increases as the diameters of the sections decrease and in particular is quite high in the cylindrical section 46 and the lower conical section 48. In the case of this second stage separator the elastic fluid does not emerge by'passage through the bottom opening 62 of the internal member 58 but rather escapes by reversal of direction of rotation into the slits 60. In this escape it is subjected to a reversal of flow of small radius with attendant production of intense centrifugal action tending to separate the finest particles.

It may be noted, furthermore, that in the interior of the member 58 a reversely rotating vortex is set up so that particles entering this tubular member 58 are further subjected to centrifugal separating action. As they separate they may flow along the walls finally dropping through the opening 62 into the lower portion of the conical section 48.

There is involved at the lower exit from the section 48 the production of a vortex which extends downwardly into the chamber 50. The particles drop-ping into this vortex are thrown outwardly and the angular velocity of this vortex is such that it is practically impossible for any particle once entering the chamber 50 to move upwardly into the section 48 to be there again entrained and carried to the outlet. In effect, therefore, there is provided a trap so that particles passing downwardly from the end of section 48 cannot return. This is particularly desirable in the case of extremely minute particles since non-uniformity of flow, which frequently occurs, is very likely to produce surges picking up separated particles and causing loss through an exit. Even larger surges occurring in the apparatus here described cannot produce any efiective disturbance inside the lower quiescent chambers which will involve reentrainment of the particles.

The elastic fluid from which substantially all particles have been removed passes into the outlet chamber 68 and thence to the exhauster through the passage 12. It may be pointed out that the exhauster is not necessary in the event that the inlet to the apparatus has sufficient pressure to provide for the necessary velocities of flow for effective separation.

It will be evident from the foregoing discussion that by changing proportions various separation characteristics may be achieved for the purpose of securing size classification of particles. In many cases where classification is not required a single stage such as the second one described above may be used alone. Alternatively, and again if classification is not required, the two stages may be identical and both of the forms of the second stage described above to insure thoroughly complete separation of even the most minute particles. Where classification is required, however, it is desirable to use two or more stages having different characteristics so that products which are separated in the successive stages may have substantially different particle size ranges.

Instead of the type of member illustrated at 58, 64 there may be used, where it is desired to avoid the separation of the most minute particles, a tubular member I8 such as illustrated in Figure which, like-the member illustrated in Figure 4, may be partly cylindrical and partly conical, this being provided with ordinary radially opening slots and with a lower exit opening 82. Such radially opening slots do not impose so great an angular change of direction of fiow of the elastic fluid and consequently do not involve the high degree of centrifugal separation illustrated in Figure 4. Furthermore, such radial slots minimize the condition of vortex flow in the outlet passage. If desired, in fact, tangentially opening slots such as 60 may be provided but opening to receive, without reversal of direction of flow, the flow from the exterior vortex. Still less separation action will occur in that case.

'While the slots of the various types mentioned should extend generally lengthwise of the outlet tube, they need not extend in axial planes but may be arranged helically in the tube with the helix wound either in the direction of the external vortex or opposite that direction.

It will be clear from the foregoing that the invention is susceptible of numerous changes depending upon results desired without departing from the principles of the invention indicated above.

What I claim and desire to protect by Letters Patent is:

A dust separator comprising a vortex chamber, said chamber including an upper substantially conical section, an intermediate substantially cylindrical section, and a lower substantially conical section, the diameter of the upper portion of said upper section being greater than that of said intermediate section and the diameter of the lower portion of said lower section being less than that of said intermediate section, a volute chamber surmounting said upper vortex section, having a generally spiral outer wall and having a tangential inlet, and an outlet tube projecting through said volute chamber and said upper vortex section, said upper vortex section having at its junction with said volute chamber a radius at least equal to the maximum radius of the volute chamber providing a transition between the vortex and volute chambers presenting only surfaces other than substantially horizontal dust accumulating surfaces, and the bottom of said volute chamber being throughout its entire cross-sectional area external to said outlet tube and in free open communication with the upper end of said upper vortex section.

NICHOLAS N. STEPHANOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Germany Oct. 2, 1936 

